Flex block



FIG. 1 is a perspective view of the flex block;

FIG. 2 is a front side view thereof;

FIG. 3 is a back side view with thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines are included for the purpose of illustrating portions of the flex block and form no part of the claimed design. 

CLAIM The ornamental design for a flex block, as shown and described. 